Composite polypropylene filaments having a high degree of crimp



United States Patent 3- 533,904 COMPOSITE POLYkROPYLENE FILAMENTS HAVING A HIGH DEGREE 0F CRIMP George Jurkiewitsch, Clifton Forge, Va., assignor to Hercules Incorporated, Wilmington, Del., a corporation of Delaware Filed Oct. 19, 1966, Ser. No. 587,780 Int. Cl. D0211 /22; D02g 3/00, 3/34 US. Cl. 161-173 3 Claims ABSTRACT OF THE DISCLOSURE Composite polypropylene filaments having at least 58 crimps per inch, an intrinsic viscosity from about 1.7 to about 3.0, a denier per filament of 22 or less, a crimp contraction of at least 50%, a stretch of at least 75%, and a recovery of at least 40% are obtained by conjugate melt spinning two or more propylene polymers having different molecular Weight distributions. The molecular weight distributions of the polymers are selected and coordinated with processing conditions including spinneret temperature, the desired filament viscosity, and drawing and relaxing conditions to obtain the desired combination of properties in the filament. Graphs are provided for selecting and coordinating filament viscosity, spinneret temperature, denier per filament, etc.

This invention relates to polypropylene filaments and filamentary yarn having a high degree of helical crimp and to a method of making same.

It is known from British Pat. No. 979,083 that selfcrimping polyolefin filaments can be produced from two polyolefin components of different viscosities by a meltspinning process wherein the molten polymers are fed separately to the shaping orifice and form filaments having the two components distributed along the length of the filaments in side-by-side or sheath-core relationship. It is also known from the investigations of others that selfcrimping polyolefin filaments can be formed similarly from two polyolefin components which have substantially the same viscosity but different molecular weight distributions.

According to British Pat. 979,083, the highest degree of crimp obtained in polyolefin filaments utilizing polyolefin components of different viscosities was 14 per centimeter (E36 per inch). In the case of the composite polyolefin filaments made from polyolefin components having different molecular weight distributions, the highest degree of crimp observed was 44 per inch.

The principal object of this invention is to provide polypropylene filaments, including monofilaments and multifilaments, having a substantially higher degree of crimp as well as other desirable properties which make it ideally suited for various applications not attractive with lower degree of crimp.

The above and other objects are achieved by the product of the present invention which is characterized by having from about 58 to about 300 helical crimps per inch, and preferably at least 100 crimps per inch, an intrinsic viscosity from about 1.7 to about 3.0, a denier per filament in the drawn yarn of 22 or less, a crimp contraction of at least 50%, and preferably at least 60%, a stretch of at least 75%, and preferably at least 100%, and a recovery of at least 40%, and preferably at least 50%.

The term crimps per inch (CPI), as used herein, is the number of helical coils per inch of a given sample of bulked fiber under zero stress. It is determined as follows.

A 100 meter skein of the fiber sample to be tested is placed in a knit tube bag, heat treated for minutes in 100 C. water and then centrifuged dry. Twenty 4- 3,533,904. Patented Oct. 13, 1970 inch lengths of the fiber sample are secured to a calibrated glass plate, in a zero stress state, the extremities of the fibers being held to the plate by double coated cellophane tape. The sample plate is then covered with an uncalibrated glass plate and the crimps present in a twoinch length of each fiber are counted. The total number of crimps in the 20 two-inch fiber lengths is then divided by 40 to obtain the average crimps per inch.

The term bulk denier, as used herein, is the weight in grams of a cm. length of a given fiber under a load of 0.01 gram per drawn denier multiplied by 10,000. It is determined by securing one end of a four-foot fiber sample, prepared as above described, loading the sample to 0.01 gram per drawn denier, marking and cutting a 90- cm. length from the loaded sample and weighting the 90-cm. length.

The term drawn denier, as used herein, is the weight in grams of a 90-cm. length of a given fiber, after being drawn under a load of 0.15 gram per drawn denier, multi plied by 10,000.

The terms crimp contraction and linear loaded shrinkage as used herein are defined as follows: Crimp contraction is the percentile expression of a particular fiber bundles ability to develop crimp while being subjected to a predetermined tensile stress. Specifically, crimp contraction is the percent change in a fiber bundles length, due to the formation of crimp in the component fibers of the bundle. The standard load stress is 5X10- grams per drawn denier.

Linear loaded shrinkage is the percent change in the length of a fiber bundle due to permanent linear contraction while being subjected to a predetermined tensile stress. The standard load stress is 5 10- grams per drawn denier.

Crimp contraction and linear loaded shrinkage are determined as follows: The given fiber sample, prepared as above described, is loaded to 0.15 gram per drawn denier and a 3 0 centimeter length of the extended fiber marked thereon. The sample is then reloaded to 5X 10 grams per drawn denier, heat treated in a circulation oven for 10 minutes at 135 C., removed and cooled for 5 minutes and the distance between the marks placed on the sample, as above, measured with the 5X10- grams per drawn denier weight still attached. This distance is represented by L, in the formulae below. The sample is then reloaded to the gauge weight of 0.15 gram per drawn denier and the distance between the marks placed on the sample, as above, again measured. This distance is represented by L in the formulae below. Linear loaded shrinkage, crimp contraction and total contraction are calculated as follows:

Linear loaded shrinkage= Crimp contraction= Total contraction=linear shrinkage+crimp contraction Also, total contraction: X 100% a 100 cm. length of the sample. Load the sample to 0.5 gram per bulk denier with the above-mentioned 0.01 gram per drawn denier weight in place. Record the elongation the 100 cm. length experiences in the first 30 seconds of loading time; remove the 0.5 gram per bulk denier and record the contracted length of the 100 cm. sample after 30 seconds. The percent stretch and recovery are then calculated as follows.

sample length (em.) after 30 see. Percent under 0.5 gram per bulk denier load 100 Percent recovery 100 sample length after 30 see. loadsample length after 30 sec. release Percent stretch Where the term viscosity is used herein, in relation to the starting polymer components or filament, intrinsic viscosity (I.V.) measured in decalin solution at 135 C., using a viscometer capillary diameter of 0.44 mm., is meant, the units of viscosity being expressed in deciliters/ gram.

In accordance with the invention, the novel filaments of the invention are prepared by (l) melt spinning two polypropylene polymers having different molecular weight distributions so as to form filaments having the two polypropylene polymers distributed along the length of the filaments as distinct components in side-by-side or sheath-core relationship, such filaments having intrinsic viscosities from about 1.7 to about 3.0, (2) drawing the filaments, and (3) relaxing the filaments to set the crimp, all under the codnitions hereinafter described. Alternatively, if desired, the relaxation step can be omitted and the filaments wound on a bobbin under tension to provide filaments having a latent crimp.

The starting materials contemplated for use in making the novel filaments herein described are highly crystalline polymers made wholly or predominantly from propylene and having differing molecular weight distributions and the same or different intrinsic viscosities. These polymers include crystalline polypropylene itself, otherwise called isotactic or stereoregular polypropylene and crystalline block copolymers of propylene with up to about 20 mole percent of ethylene. The molecular weight distribution of the polymers is expressed in terms of a dispersion coefficient Q, the value of Q being the ratio of weight average molecular weight, Mw, to number average molecular weight Mn. The values of Mw and Mn can be determined as described in an article by Shirley Shyluk, J. Poly. Sci.

62, 317 (1962), entitled Elution Fractionation of Atactic and Isotactic Polypropylene.

The dispersion coeificient Q of the polymer having the higher Q value should be at least 4 and the dispersion coefficient of the polymer having the lower Q value should be at least about 2.5. The difference between the Q values of the polymer components should be at least 1.0 and preferably at least about 2.0 in order to obtain the highly crimped filaments of the invention. Polymers having Q values up to about 20 can be used.

Polymers having different molecular weight distributions can be produced in several ways. Thus, thermal degradation of polypropylene from a higher to a lower viscosity will cause a narrowing of the molecular weight distribution, the product then being used as one component of a composite filament, the other component being, for example, an undegraded polymer or a polymer which has been subjected to a lower degree of degradation. Alternatively, a polymer, a portion of which has been chain terminated during polymerization as, for example, by the use of hydrogen as chain terminator, and which has a broad molecular weight distribution, can be used as the second component. The ratio of the component having the broader molecular weight distribution to the component having the narrower molecular weight distribution can be varied from about 1:1 to about 3:1, the self-crimping effect obtained over this range being somewhat dependent upon the difference between the Q values for each component. Thus, as the ratio is increased, the difference in Q values should also be increased.

In selecting propylene polymer components which can be spun into filaments having intrinsic viscosities from about 1.7 to about 3.0, allowance must be made for any degradation of the polymer components which occurs while they are being processed into filaments. The amount of degradation primarily depends on the temperature of spinning and the particular stabilizer system, if any, used. Thus, degradation is greatest at higher spinning temperatures. However, by use of stabilizers, degradation can be more or less reduced depending on the effectiveness of the particular stabilizer system used. It is possible, therefore, to use polymer components of relatively high viscosities, e.g., 10.0 or even more, where considerable degradation is to be expected. On the other hand, where an effective stabilizer is used and only a small amount of degradation is expected, polymers having intrinsic viscosities as low as 1.9 can be used. In most cases, it is preferred to use polymer components having intrinsic viscosities from about 2.0 to about 3.2.

A satisfactory crimp level of the degree herein contemplated can be obtained by using polymer components having the same or different viscosities provided the Q values of the components differ by at least 1.0. Thus, polymer components having viscosities which differ by, for example, 0.9 have given satisfactory results.

The component polymers may contain up to about 20% or more by weight of other substances such as heat and light stabilizers, ultraviolet light absorbers, antacids such as calcium soaps, phenolic and other antioxidants, compounds capable of decomposing peroxides, phosphites, and the like, as well as other materials such as pigments, dyes, fillers, and the like.

The polymer components, of the type hereinabove described, are separately melted and fed to a spinneret and the separate streams brought together as they pass through the spinneret orifice. Spinning should be carried out at temperatures from about 240 C. to about 320 C., the particular temperature selected depending upon the viscosity desired in the filament, the denier per filament, the difference in Q values of the polymer components, and the level of crimp desired. Thus, it has been found that for a given intrinsic viscosity, denier per filament and difference in Q values, crimps per inch increase in number as the temperature decreases but that this tendency reaches a maximum at a certain lower limit of temperature and then reverses as still lower temperatures are used. It has also been found that crimps per inch increase with viscosity at a given level of temperature, difference in Q values, and denier per filament. Further, at a given level of temperature, difference in Q values, and intrinsic viscosity, crimps per inch increase as the denier per filament decreases. And, finally, crimps per inch increase as the difference in Q values of the polymer components increases. It is necessary, therefore, that filament viscosity, spinning temperature, and denier per filament be maintained within certain limits and properly coordinated with each other and with the difference in Q values of the polymer components in order to obtain the novel filaments and yarns herein described and claimed.

The graphs in the accompanying drawings are designed to illustrate various aspects of the invention. Referring first to FIG. 1, the curve shows crimps per inch (CPI) as a function of spinneret temperature for a filament viscosity of 1.7, a denier per tfilament (DPF) of 3.0 and Q values of the polymer components of 8.0 and 4.0.

As will be evident from this curve, for a given intrinsic viscosity, denier per filament and difference in Q values of the polymer components, crimps per inch increase as the temperature decreases until a certain temperature is reached at rWhlCh point this tendency is re versed. While the curve in FIG. 1 is based on a filament viscosity of 1.7, it will be apparent from what has been said hereinabove that curves for higher filament viscosities, other conditions remaining the same, will each be above the corresponding curve in FIG. 1. Curves for greater differences in Q values of the polymer components will likewise be above the curve in FIG. 1.

In the graph of FIG. 2, spinneret temperatures are plotted against filament viscosities, 'the area A enclosed within the polygon representing the operative ranges of spinneret temperatures and filament intrinsic viscosities which can be utilized to obtain the results herein contempated.

In FIG. 3 of the drawing, crimps per inch are plotted as a function of denier per filament for various intrinsic viscosities within the scope of the invention. The polymer components utilized to obtain the data for FIG. 3 had Q values of 8.0 and 4.0, respectively. The area enclosed by the solid lines AB, BC, CD and DA, and designated I, represents the preferred working area for obtaining a desired crimp level for a given denier per filament and filament intrinsic viscosity within the range 1.73.0 which has been found to be critical for obtaining the high degree of crimp and other desirable properties in accordance with the present invention. The. dotted line passing through the area I is based on a filament intrinsic viscosity of 2.5.

The area designated I can be further extended to include the area enclosed by the solid lines AE, EB and BA designated II by properly selecting spinneret temperature (FIG. 2) for given values of filament intrinsic viscosity and denier per filament (FIG. 1). The area I can likewise be extended above the line CD to obtain higher CPI by using polymer components having greater differences in Q values.

In using the graphs to obtain a filament, the end use application of which requires a filament intrinsic viscosity of 1.7 and a denier per filament of 5, we find from FIG. 3 that about 94 crimps per inch would be obtainable. By reference now to FIG. 2 which covers temperatures and viscosities for crimps per inch from 58-315, we find that .98 crimps per inch can be obtained by selection of a temperature from the area A corresponding to an intrinsic viscosity of 1.7. For maximum crimp formation under the indicated conditions of intrinsic viscosity, denier per filament, and difference in Q values of the polymer components, a temperature about midway between the upper and lower extremes corresponding to an intrinsic viscosity of 1.7 should be chosen.

In the above example, ifa filament texture characterized I by a lower degree of crimp, e.g., 80 crimps per inch is desired, a higher spinneret temperature should be selected as will be evident from the relationship between spinneret temperature and crimps per inch shown by the curve in FIG. 1 limited, however, to the working area designated A in FIG. 2. It will be noted that this particular combitemperature in the upper portion of the range corresponding to an intrinsic viscosity of 1.7 (FIG. 2) should be used.

After spinning, the filaments are taken up at a speed of from about 500 to about 2000 meters per minute and then drawn utilizing a draw ratio from about 1.5 to about 4.0. Preferred draw ratios are from about 2.0 to about 3.2. Drawing must be carried out under temperature conditions not exceeding 100 C. and preferably not exceeding 70 C.

Drawing can be carried out on conventional equipment using feed and draw rolls, the latter rotating at a sufiiciently higher rate of speed than the former to accomplish the desired draw. In order to come within the critical temperature limits for drawing, the feed roll temperature should not exceed about 70 C. and the draw roll temperature should not exceed about 100 C. and can be as low as room temperature.

From the draw roll the filament can be passed to a relaxation roll which should be maintained at temperatures from about room temperature to about 140 C. for maximum crimp formation and permanency. Alternatively, in process relaxation can be carried out by conventional and modified means such as a hot air chamber, hot plate, radiation heating devices inserted between the draw and relaxation rolls, etc., to accomplish spontaneous crimp development and effective heat setting. The crimp level can be controlled conveniently by adjusting the speed of the relaxation roll in a range from about 100% to about of the draw roll speed and the temperature of the filament between the draw and relaxation rolls sufficiently high, but below the melting point of the filament, to obtain the desired relaxation. Relaxation can also be carried out in a hot air oven at about 135 C. for about 30 minutes.

If desired, the relaxation step can be omitted and the drawn wound on a bobbin under tension to produce yarn having a latent crimp. This yarn can then be formed into fabric as by knitting or weaving and the fabric then given a treatment, e.g., a scour and heat treatment to develop the crimp.

The following examples will illustrate the invention.

EXAMPLES 1-6 Melt spinning apparatus provided with means for separately supplying two molten polymers to a spinneret at independently controllable rates was used to produce composite filaments from six pairs of propylene polymers each containing heat and light stabilizers to minimize polymer degradation. The component polymers joined at the spinneret orifices in a 1/1 ratio to produce filaments of the side-by-side type. The spinnerets used had 36 orifices of 0.020 inch diameter and the denier per filament of the spun filamentary yarns was adjusted for 3.0 draw ratio. Other spinning conditions, etc., are given in Table I below.

nation of intrinsic viscosity of 1.7, denier per filament of 5 and crimps per inch of '80 does not fall within the area designated I in FIG. 3. However, from the area II of FIG. 3, we know that 80 crimps per inch is obtainable at 5 denier per filament and from the relationship of tem- The spun yarns were collected on rigid bobbins and drawn using a feed roll temperature of C. and a draw roll temperature of 100 C., the draw roll speed being 300 m./min. From the draw roll the drawn yarns passed to a relaxation roll maintained at room temperature and perature and crimps per inch shown in FIG. 1 that a operated at a speed equivalent to the draw roll speed and were then wound on bobbins. The draw ratio and properties of the yarns are given in Table II below.

(1) conjugate melt spinning propylene polymers having intrinsic viscosities of at least about 1.9, and

TABLE II Drawn dcnier Crimp Draw Filament per Tenacity, Crimps contraction, Stretch, Recovery, ratio viscosity filament g./denier per inch percent percent percent;

Ex ample N 0.:

EXAMPLES 7-12 dispersion coeflicients Q from about 2.5 to about 20, the dispersion coefficient Q of the polymer havmg l5 Yarns were prepared as in Examples 16 except that the high Q value being at least 4 and the difference 1n different viscosities, Q values, etc., were used. These and Q values b t en the polymers being at least 1.0, other conditions of spinning are set forth in Table III the temperature of spinning being from about 240 below. C. to about 320 C.,

TABLE III Spinneret temper- WInd-up Polymer Drawn ature, Delivery, speed, viscosities Qvalues denier g./nnn. m./m1n.

Example No.1

7 4. 0/0. 0 108/6 270 11. 25 11. 25 678 4. 0/0. 0 00 0 270 11. 25/11. 25 810 4. 0 5. 0 10s 9 270 11. 25/11. 25 07s 4. 0/0. 0 105 12 270 11. 25 11. 25 07s 4. 0/0. 0 108/18 270 11.25/11. 25 07s 4. 0 0. 0 108/30 270 11.25 11. 25 07s The spun yarns were collected and then treated as in Examples 1-6. The draw ratio and properties of the yarn are given in Table IV below.

(2) selecting filament viscosity and spinneret temperature from the area designated A in FIG. 2, (3) drawing the filament at a draw ratio from about TABLE IV Drawn denier Crlmp Draw Filament per Tenacity, Crimps contraction, Stretch, Recovery, ratio viscosity filament g./denier per inch percent percent percent Example No.:

By virtue of the high degree of crimp and other desirable properties, such as improved crimp contraction, stretch, and recovery from load, the filaments and/or filamentary yarns of the invention are eminently suitable for use in the manufacture of woven goods of stretch fabric type such as used in sport wear type fabrics, e.g., trousers, jackets, shirts, foundation fabrics and garments, athletic fabrics, swimming suits, dresses, suits, covering fabrics and upholstery fabrics, specialized industrial applications, and knit fabrics, such as hosiery, and special apparel applications. Such fabrics are characterized by improved stretch and recovery, abrasion resistance and resiliency, easy care properties and tactile properties. The improved stretch and recovery properties of the highly crimped filaments of the invention make them uniquely applicable to use in knit goods where dimensional stability and recovery from load are critical such as in hosiery.

What I claim and desire to protect by Letters Patent is:

1. A composite polypropylene filament having at least 58 crimps per inch, an intrinsic viscosity from about 1.7 to about 3.0, a denier per filament of 22 or less, a crimp contraction of at least 50%, a stretch of at least 75 and a recovery of at least 2. The process of producing a composite polypropylene filament having at least 58 crimps per inch, an intrinsic viscosity from about 1.7 to about 3.0, a denier per filament of 22 or less, a crimp contraction of at least a stretch of at least 75%, and a recovery of at least 40% which comprises 1.5 to about 4.0 and at a temperature not in excess of C., and

(4) relaxing the drawn filament at a temperature from about room temperature to a temperature below the melting point of the filament.

3. The process of claim 2 wherein the filament viscosity, spinneret temperature and denier per filament are selected from the area designated A in FIG. 2 and from the areas designated I and II in FIG. 3.

References Cited UNITED STATES PATENTS 3,438,193 4/1969 Kosaka et a1 264171 2,439,815 4/1948 Sisson 264-168 2,443,711 6/1948 Sisson 264-168 3,093,444 6/1963 Martin 264168 3,399,259 8/1968 Brayford 264171 3,408,277 10/ 1968 Martin et a1 264168 FOREIGN PATENTS 40/9,533 5/1965 Japan.

ROBERT F. BURNETT, Primary Examiner R. H. CRISS, Assistant Examiner US. Cl. X.R.

3 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,533,904 Dated October 13 1970 Inventor(s) George Jurkiewitsch It is certified that: error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 10 of printed patent, "Percent" should read Percenlto stretch-- Column 6, line 37 of printed patent, after the word drawn --yarnshould be inserted Column 8, line 16 of printed patent (in the claims),

"high" should read -higher-- SIGNED Mu REAUEP (S Atteat:

Edward M. Fletcher, In WILLIAM E- SCIHUYLER m c L Attesfing Officer Commissioner of Patents J 

